Stockholders' Equity - Dividends (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Equity [Abstract]
Cash Dividends Declared Per Common Share (in dollars per share)	$ 0.76	$ 0.72	$ 0.56
Cash Dividends Declared, Total	$ 209	$ 209	$ 80
Cash Dividends Declared, Unpaid at Fiscal Year End	$ 53	$ 51	$ 20